The Chainsmokers and Halsey’s hit “Closer” was one of the biggest songs of 2016, sitting at Number One for 12 weeks. The song’s exuberant pulse can be traced back to the teenaged Chicago duo Louis the Child, who helped co-write the song and imbued it with hints of an emerging sound being called “future bass.”

A still-codifying genre, future bass takes the ecstatic drops of dubstep or trap, but provides a warm bounce rather than a lumbering bruteness. Basslines are provided by harsh, detuned synths that buzz and purr instead of gulp and whomp. “In the Name of Love,” a maximalist take on the idea, scored Dutch producer Martin Garrix, along with the singer Bebe Rexha, a Top 40 hit. Artists like Australia’s Flume and masked mystery-man Marshmello are top-tier festival breakouts who also deploy the style.

“It’s still pretty mind-blowing to see how far it’s gone,” says Freddie Kennett of Louis the Child, about “Closer.” He co-wrote the song on a bus with Drew Taggart of the Chainsmokers while the two groups were on tour – bandmate Robbie Hauldren missed the session since he was prepping for a final exam. Taggart finished up the song, added alt-pop star Halsey and the result was more than just a hit, it was a breakout for an emerging sound. Even if Kennett’s name is buried in the credits, the song’s half-step lurch sits closer to Louis the Child’s own work than the brash electro-pop of their older co-writing partners.

“Back in the day it was call ‘chill trap’ or ‘melodic trap,'” says Hauldren, “and then it turned from this 140 [bpm] chill trap into half-step beat, brought up a little bit more with the filtered chords that are super reverb[ed].” The gentler textures and rhythmic differences separate it from trap music’s brief bout with mainstream success, exemplified by Baauer’s viral hit “Harlem Shake” and DJ Snake’s “Turn Down for What.” Pulling even further back, the style recalls the disparate British post-dubstep from producers like Joker, Hudson Mohawke and James Blake, who all dealt in discovering new textures away from the original dubstep template.

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“The first time that I heard future bass was when Flume put out the ‘You and Me’ remix,” says Whethan, a 17-year-old Chicago-based future bass producer. That particular remix, also cited by Louis the Child, laid out the genre’s blueprint with its mellow, instead of abrasive drop, and prominent use of vocals. Last year, Flume released his second album, Skin, which won a Grammy for Best Dance/Electronic Album and produced his first Billboard hit, “Never Be Like You,” eventually peaking at Number 20.

Though he thinks little of genre limitations, Whethan isn’t pushing back against the genre label either. “A lot of music I have coming out in the future will probably be considered future bass,” he says, “but [it] has a lot of indie and alternative roots.”

That passion for guitar-focused indie music is a through line for a number of future bass producers. “I realized I couldn’t do something new with my guitar,” says Dutch producer San Holo on what directed him towards electronic music production. While studying guitar in school, he took production courses and grew interested in rap then trap, but shifted again towards future bass’ bright melodies and upbeat chords. It’s become his signature sound, with his recent “Light” hitting Number 14 on Billboard’s Hot Dance/Electronic chart.

“I wrote ‘Light’ about a half a year ago, when I really wanted to see the light because I was kind of lost,” says Holo. The producer got serious about his solo career after ghost-producing for other artists and seeing them find success from his work. Recently, like other future bass producers, he’s moving away from strictly instrumental music. “I try to let my melodies have a voice themselves,” says Holo, “[but] I notice that a human element in a song can be really touching to people.”

“Tracks that are vocal-driven doing really well,” says Geronimo, Sirius XM’s Vice President of EDM Music Programming looking back at 2016. “It seems like listeners, our subscribers, and fans are relating more to songs that are more vocal driven.”

The positive reaction to the music is mirrored in the artists themselves, who are embracing a style that opens up instead of closes creative possibilities. “You can call Flume ‘future bass’ or Wave Racer ‘future bass,'” says Kennett, observing the style’s diversity. “I love how you can do that … but sound completely different.”